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In 1986, the Centers for Disease Control and Prevention (CDC) initiated a program of national surveillance of pregnancy-related deaths. It is serially updated and can be accessed at: www.cdc.gov/reproductivehealth/maternalinfanthealth/pmss.html. Using this database, Creanga and colleagues (2015) reported an increase in the maternal mortality rate from 7.2 per 100,000 in 1987 to 17.8 per 100,000 in 2009. It is also clear from this report that hemorrhage remains a significant cause of pregnancy-related deaths, accounting for 11.4 percent of such deaths from 2006 to 2010. This is despite widespread recognition of the consequences of obstetric hemorrhage and the availability of modern blood-banking techniques. Notably, the United States is one of the few countries worldwide that has not reported a decline in maternal mortality rates but instead has shown a significant rise. One worrisome trend was the marked racial disparity in pregnancy-related mortality rates. In data from 2006 to 2010, white women suffered 12 deaths per 100,000 births, whereas the rate for black gravidas was 36.4 deaths per 100,000 births (Creanga, 2015). Also disturbing is that approximately 90 percent of maternal hemorrhage-related deaths have been considered potentially preventable (Berg, 2005; D'Alton, 2014).
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In addition to mortality, postpartum hemorrhage can lead to severe postpartum morbidity. In a multicenter surveillance study of postpartum hemorrhage from Brazil, Rocha Filho and coworkers (2015) reported that the hemorrhage-related incidence of severe maternal morbidity approximated 3 events per 1000 live births. Significant or severe postpartum hemorrhage is estimated to complicate 2 to 4 percent of vaginal deliveries and 6 percent of cesarean births (Combs, 1991a,b; Klapholz, 1990).
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DEFINITION AND RISK FACTORS
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Although postpartum hemorrhage has always been one of the leading causes of maternal mortality and morbidity, no universally accepted definition for this complication is recognized. Pritchard and associates (1962) quantitatively measured the blood loss in women who had a vaginal delivery, had a repeat cesarean delivery, or underwent repeat cesarean delivery with hysterectomy (Table 29-1). In a review of postpartum blood loss, Gahres and colleagues (1962) reported a mean loss following vaginal delivery of 450 mL for all series. Traditionally, postpartum hemorrhage has been defined as blood loss exceeding 500 mL following vaginal delivery and exceeding 1000 mL following cesarean delivery.
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Several problems muddy this definition. First, clinical estimates of blood loss are notoriously inaccurate, and blood loss is often underestimated and underappreciated. Another major problem is that blood loss often approaches or exceeds these amounts without clinical consequences.
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Another criterion used to define postpartum hemorrhage is ...